1. Field of the Invention
The invention relates to a method and an apparatus for determining a variation in criteria, parameters and/or command values of an automatic piecing operation at an automatic piecing apparatus of an automatic spinner, in which a piecer and/or a length of thread in which the piecer is located upon a resumption of winding after a piecing operation in which the spun yarn is received, is measured in accordance with a criteria of diameter or diameter per unit of length and is evaluated with a view to improving the piecer, with at least one sensor disposed along the thread travel.
2. Description of the Related Art
A method and an apparatus for monitoring piecers in an open-end spinning system are known, for instance, from U.S. Pat. No. 4,825,632 to Raasch et al. In the length of thread that contains the piecer, the diameter values are measured relative to the longitudinal axis of the thread, stored electronically in memory in an apparatus, and compared with comparison values in a comparator in that device. The comparison is used to purposely derive options for intervention in order to improve future piecers in an apparatus connected to the output side. The apparatus includes a device for metering quantities of piecer fibers, which determines the on time of a switch of a sliver draw-in device for producing the next piecer based on the result of a comparison, so that a suitable quantity of fiber can be pre-stored in a rotating fiber collector. Average values formed in an average former from various measurements can be used for comparison.
However, the criteria used and the variation thereof are not adequate for quickly and reliably finding the advantageous piecer profile for the most varied types of yarns and fiber materials, or even for attaining good piecing results that vary within desirably narrow limits.